Montly prepair plan somehow not working

I changed to a 23GB at 4 GB speed plan of 25 Cad last month, but somehow i couldnt use the mobile data at all, im using a xiaomi phone.
I have asked someone in the Koodo shop to assist me with this, they checked and everything is normal, they didnt find anything wierd with my sim, but they also dont know why my phone couldnt use data from the plan as well..
I have to temporarily disable my auto pay to avoid being charged for nothing at all for now.
Can someone help me with this? Thanks!